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保护接地要注意哪些问题?工作接地要注意哪些问题?

问答题
2022-05-08 10:53
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正确答案
保护接地要注意的问题:
①电气设备都应有专门的保护导线接线端子(保护接线端子),并用‘’符号标记,也可用黄绿色标记。不允许用螺丝在外壳、底盘等代替保护接地端子。
②保护接地线用粗而短的黄绿线连接到保护接地端子排上,接地排要接入大地,接地电阻要小于4。
③保护接地不允许形成环路。
④设备的金属外壳良好接地,是抑制放电干扰的最主要措施。
⑤设备外壳接地,起到屏蔽作用,减少与其他设备的相互电磁干扰。
工作接地要注意的问题:
①设备的接地不能布置成环形,一定要有开口,保护接地也遵循这一原则。
②采用光电隔离、隔离变压器、继电器等隔离方法,切断设备或电路间的地线环路,抑制地线环路引起的共阻抗耦合干扰。
③设备内的数字地和模拟地都应该设置独立的地线,最后汇总到一起。
④工作地浮地方式只适用于小规模设备和工作速度较低的电路,而对于规模较大的复杂电路或者设备不应该采用浮地方式。
⑤电柜中的工作地线、保护地线和屏蔽地线一般都接至电柜中的中心接地点,然后连接大地,这种接法可使柜体、设备、屏蔽地和工作地保持在同一电位上,保护地和屏蔽地最终都连在一起后又与大地连通。

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